Signature of Antimatter Detected in Lightning
wired.com
wired.com
That actually sounds like bremsstrahlung x-rays, not gamma rays. They have very different energy spectra due to their origin. Although you can also slow down the electrons by first producing an electron-positron pair, and then the positron will decay into two gammas.
http://www.scientificamerican.com/article.cfm?id=x-rays-abou...
Pilots reported red and blue jets and sprites for a long time but noone believed them.
http://www.islandnet.com/~see/weather/elements/bluejets.htm
How thunderstorms work is still poorly understood. This building evidence is exciting a lot of new research and ideas. A lot of people are impressed that the earth can generate gamma rays of higher energy than those from the sun.